Load Command Line Options from a file

Direct command line can get too long:

weed -logdir=../mlog master -mdir=../mdir -peers=192.168.126.5:3333,192.168.126.16:3333,192.168.126.18:3333 -port=3333 -defaultReplication=001

You can put these command line options into a configuration file :

# master.conf
logdir=../mlog
mdir=../mdir
peers=192.168.126.5:3333,192.168.126.16:3333,192.168.126.18:3333
port=3333
defaultReplication=001

then refer it as

weed master -options=master.conf

Order of precedence of this flag, it is borrowed from https://github.com/namsral/flag with some customized for weed:

1. Command line options
2. Environment variables with `WEED_` prefix
3. Configuration file
4. Default values